Dew busting

I had always got by without a dew heater system or shield and just put up with it, but during recent observing sessions I got so fed up with the Telrad and, especially, the secondary mirror dewing up (which brought sessions to a premature end because there is no way of getting dew off a mirror without resorting to using a hair dryer, which would be unbelievably loud in the dead of night!), I decided to do something about it.

I have invested in a dew-busting system, which consists of a dew heater controller, a Telrad dew heater and a secondary mirror strip, from Astronomia in Surrey. I am waiting for the secondary heater (a Kendrick split secondary heater) to arrive, as Astronomia didn’t have one in stock. The dew controller is powered by a 12 volt power supply, in this case a power supply with inverter, which is intended by its manufacturer to jump start cars and supply back up power for caravans and boats, which I got from a car parts supplier.

AWR dew heater controller


Telrad dew heater


The dew heater fitted to the Telrad


While I was spending money (the proceeds of the sale of my 12 inch) I decided to get a TeleGizmos scope cover from the Widescreen Centre. It was expensive but worth it to protect the scope. The particular one I got is designed to fit 18-20 inch f/4.5 truss dobs, with a bit of room to spare. It should also help keep condensation off the primary mirror because it will keep the scope cool even when the shed heats up during the morning, as it will do on all but the coldest winter day.

Something else I am going to try in order to keep condensation off the mirror is to put a heated mat, of the sort used to keep reptiles’ tanks warm, in the rocker box. The mat won’t get hot but should keep the mirror from looking like it was dumped in a swimming pool each morning.


In the current edition of the local paper, in the Nature Notes section, there is a piece by Helen Shaw, all about light pollution and its effects on wildlife, titled ‘We are in the dark over light pollution‘. It’s good to see that people other than amateur astronomers are concerned about this as it shows it has far-reaching effects and doesn’t just affect a tiny minority of the population. At an event our society attended back in August, the general public were pretty clued-up about light pollution and nearly everyone agreed that it needs to be addressed, so we are getting somewhere. I feel as if someone else’s lights trespassing is the equivalent of cigarette smoke being blown in your face and just as anti-social – I got told off for using that analogy on Cloudy Nights a few days ago (I have no idea why) but I make no apologies for it as I think it is a good one. If not cigarette smoke, then excessive noise, perhaps.
I have sent in the following, for the letters section, and it will be interesting to see what the reply will be – if they publish it. I am not given to writing to the press, especially local press, but light pollution is something I feel strongly about enough to do so.

I was pleased to see Helen Slade’s Nature Notes article on light pollution in the October 7th IWCP. Light pollution is a problem which has been allowed to get out of hand over the years, to the extent that an ugly orange glow hangs above our towns and cities from street lighting.
All that orange glow hanging over Newport, Sandown, Shanklin, Ryde, etc, at night represents our council taxes – and electricity – being wasted by light being shone into the sky where it is not needed, rather than down onto the ground where it is. In this age of energy prices rising all the time and with concerns over CO2 emissions, surely this can’t be allowed to continue?
Light pollution also results from badly-directed security lights and other lighting fixtures on homes and businesses, fixtures which have proliferated over the past couple of decades, and a lot of excess light spills onto other people’s properties and onto roads. If you want to illuminate your property no-one is saying you can’t but, please, just keep it to yourselves. We all need to see where we are going, but zillion-watt security lights shining across roads and into neighbours’ gardens is just overkill. Also, light trespass (light nuisance) is also actually against the law, as of April 2006.
Amateur astronomers, naturalists, environmentalists and people who would just like to see a natural night sky without hideous and intrusive artificial lighting don’t want to turn off the lights completely. We all know that some light is needed but only where it is most effective, which is downward onto the ground and not up into the sky or shining onto other people’s property.
People tend to think that lots of light equals safety. It doesn’t, particularly if you’re dazzled by misdirected lighting. Neither does it reduce crime. Criminals and people indulging in anti-social behaviour don’t have better night vision than law-abiding people, they need light to see, too.
Also, according to a report in the Independent newspaper recently, light pollution can affect property prices because people don’t want to live in an excessively-lit area.
However, it does seem that light pollution is beginning to be recognised as the anti-social and unpleasant thing it is and it is good to see that more people are becoming aware of the problem.
More information can be found at the Campaign for Dark Skies: and also from the Campaign to Protect Rural England: (I am not, by the way, a representative of either CfDS or CPRE).

By the way, here is a link to the Independent article: ‘Homebuyers are looking for splendid isolation and a pristine view of a star-filled sky